The 1970 Tonghai earthquake occurred on 4 January 1970 in Tonghai County, Yunnan province, China. The rupture originated on the Red River fault, which had not experienced an earthquake above magnitude 7 since 1700. The earthquake had a magnitude of 7.7 and killed at least 15,000 people, making it one of the deadliest in its decade. The tremor caused between US$5 to $25 million in damage, felt over an area of 8,781 km² (3,390 sq mi).